Evaluation of protein C and protein S levels during oral anticoagulant therapy.

A number of workers have examined protein C in relation to other vitamin K dependent factors during warfarin therapy and successfully identified protein C deficient patients by ratio calculation. However, protein S deficiency has not been addressed in this manner. This study compares protein C and protein S by functional and antigenic determination with procoagulant factors of similar half life (Factors VII and II) in an attempt to identify protein C and protein S deficient patients whilst on oral anticoagulant therapy. Procoagulant and anticoagulant factors were compared by linear regression in a population of normal blood donors and patients on stabilized warfarin therapy to obtain expected values for protein C and protein S dependent upon FVII and FII levels, respectively. Observed over expected values for protein C and protein S were calculated for individual patients and normal ranges derived. Comparison of similarly calculated observed over expected protein C and protein S ratios with these normal ranges successfully identified known protein C and protein S deficient patients who were taking warfarin at time of testing.

Effect of high physiological levels of factor VIII:C and factor V on rate of generation of thrombin activity in vitro.

Increased plasma FVIII:C concentrations occur in several conditions, including diabetes, but whether this leads to clinically relevant hypercoagulability is uncertain. Accordingly, we investigated the effects of increasing FVIII:C levels on coagulation in vitro using a computer-assisted measurement of thrombin activity. Defibrinated plasma was activated with kaolin, thrombin activity measured using the chromogenic substrate S2238 and time to generate 50% maximal thrombin activity (T50) recorded in seconds. Increasing FVIII:C levels from 100 to 350% significantly reduced T50 (mean +/- SD) from 91 +/- 3 to 64 +/- 6.2 s (P < 0.001, n = 6), and T50 correlated inversely with FVIII:C (r = -0.884, P < 0.001, n = 36). Increasing FV concentrations resulted in an additive effect with high FVIII:C levels on the rate of thrombin generation. The results showed that increasing plasma FVIII:C and FV concentrations accelerate rate of generation of thrombin activity independently, and in an additive manner.

Thrombin activity by intrinsic activation of plasma in-vitro accelerates with increasing age of the donor.

Thrombotic diseases increase in incidence with advancing years and this might be partly due to an increased propensity for fibrin formation in older individuals. Accordingly we decided to investigate whether the time taken to generate 50% thrombin activity in vitro varied with the age of the plasma donor. Coagulation was initiated in defibrinated, diluted plasma by contact activation and thrombin activity measured using the chromogenic substrate, S2238. The rate of thrombin generation was assessed by measuring the time taken to reach 50% maximal activity (T50/s). There was a highly significant negative correlation between T50 and age, T50 declining from 93 s at 19 years to 71 s at 65 years (r = -0.637, p less than 0.0001). A strong negative correlation was demonstrated between T50 and FVII level (r = -0.415, p = 0.0007) and FVIII:C level (r = -0.465, p = 0.0001). Although FVII concentration correlated with age (r = 0.307, p = 0.014) no relationship was seen between age and FVIII:C. These data suggest that coagulation rates in plasma accelerate with age.

The lupus anticoagulant in systemic lupus erythematosus.

The lupus anticoagulant was found in six of 41 unselected patients with systemic lupus erythematosus (14%). Three of these six patients had episodes of thrombosis. Thrombosis occurred in only one patient in the remainder of the series without the lupus anticoagulant. The lupus anticoagulant should be considered as one of the criteria for the diagnosis of systemic lupus erythematosus, and it may be a useful marker for those patients at risk from thromboembolism. It should be looked for in young adults with thrombotic episodes.

Urinary fibrin/fibrinogen degradation products in transitional cell carcinoma of the bladder.

Urinary fibrin/fibrinogen degradation products (FDPs) were measured in 210 specimens from 174 patients with newly or previously diagnosed transitional cell carcinoma of the bladder. They were detected in 94% of patients with deeply invasive bladder tumours (pT2-4) compared with 17% of superficial tumours. Microalbuminuria (greater than 50 micrograms/g creatinine) was also found in 80% of patients with pT2-4 lesions. Both were compared with urine cytology. Urinary FDPs are markers of bladder tumour invasion. Our results suggest that urinary FDPs are not of value in screening for the presence of bladder neoplasia but their role may be in following patients with superficial bladder tumours to detect those tumours which become invasive. The mode of excretion of the FDPs in the urine is discussed.

Intra-operative activation of coagulation--a stimulus to thrombosis mediated by vasopressin?

Vasopressin infusions in normal volunteers that produce concentrations in plasma comparable to those seen during stress, cause an increase in plasma factor VIII and shortening of the euglobulin clot lysis time (ECLT). We have investigated the relationship between endogenous vasopressin (aVP) release and haemostatic function in 7 patients undergoing major abdominal surgery. Blood samples were taken at nine intervals during the operative procedure. Plasma aVP levels peaked at median values of 51 pg/ml during bowel manipulation and remained elevated on the first post-operative day. Following, and in close temporal relationship with the rise in aVP there were increases in factor VIII coagulant activity, the ristocetin co-factor, von Willebrand antigen, plasminogen activator activity (10(6)/ECLT2) and fibrinopeptide A concentrations with shortening of the activated partial thromboplastin time. The relationship was similar to that seen following infusion of aVP in human volunteers. The results are consistent with the hypothesis that aVP is an important mediator of changes in haemostatic function which accompany stress and might contribute to the thrombotic risk associated with surgical operations.

Does hypernatraemia promote thrombosis?

Hypernatraemic states are associated with an increased risk of thrombosis. To examine the relative contributions of sodium and vasopressin, we infused hypertonic saline in 11 male volunteers and measured the effect on factor VIII (FVIII), euglobulin clot lysis time (ELT) and fibrinopeptide A (FPA) generation. Samples were taken pre-infusion, hourly during a 3h infusion of 450 ml 6M saline and one hour after the infusion had stopped. Mean plasma osmolality (SEM) rose from 287(0.7) to 302(10) mOsm after 3h (p less than 0.01). Plasma vasopressin concentrations rose from 1.0(0.3) to 4(0.94) pg/ml over 3 hr (p 0.01). Plasminogen activator activity (10(6)/ELT2) rose from 65(10) to 372(55) units (p less than 0.001). There was a highly significant correlation between plasma osmolality and plasminogen activator activity (r = 0.5 p less than 0.0001). FPA generation time shortened from 7.2(0.4) to 5.4(0.6) min after 2h and 5.3(0.6) after 4h (n = 6). Values for FPA after 4 min incubation steadily increased from 5.8(1.2) to 14.3(4.6) pmol/ml during the infusion but differences failed to achieve statistical significance. FVIIIC (1 stage) remained constant at 75(5.5%) during the infusion. There was a small and statistically insignificant increase in FVIII RiCof after 3h and FVIII RAg decreased slightly. The results suggest that hypernatraemia and increasing plasma aVP concentrations produce changes in haemostatic function consistent with a hypercoaguable state. The mechanisms for the effect are unclear. These changes in haemostatic function might contribute to the thrombo-embolic complications of conditions such as hyperosmolar coma in diabetes mellitus or severe heatstroke in which degrees of hypernatraemia occur.

Effects of physiological concentrations of vasopressin on haemostatic function in man.

Plasma concentrations of vasopressin (aVP) attained under conditions of stress were simulated by infusing four volunteers with 0.25, 0.5, 1.0 and 2.0 pressor units of aVP over 1 h (units/h). Three subjects had all four infusions and one received only 1.0 unit/h. Blood samples were taken for assay of factor VIII coagulant activity (FVIIIC), factor VIII related antigen (FVIIIRAg), the ristocetin cofactor (FVIIIRiCof), euglobulin lysis time (ELT) and aVP concentrations before infusion (time 0) and every 20 min for 80 min. Fibrinopeptide A (FPA) generation time was measured at time 0, 60 and 80 min. At infusion rates of 0.25 unit/h median aVP levels peaked at 6.5 pg/ml and there was no change in FVIII or FPA generation time, and plasminogen activator activity (10(6)/ELT2) rose from 100 to 400 units. At 1.0 unit/h, aVP levels rose to 25.4 pg/ml, FVIIIC rose by 160% and activator activity from 87 to 360 units. At 2.0 units/h, aVP concentrations reached 83 pg/ml, there was an increase in all modalities of FVIII and activator activity rose from 251 to 452 units. FPA generation time shortened and circulating plasma levels of FPA were increased. There was a highly significant correlation between the percentage increases in all three components of FVIII and plasma aVP levels (FVIIIC: r = 0.87, P less than 0.0001; FVIIIRAg: r = 0.61, P less than 0.0001; FVIIIRiCof: r = 0.80, P less than 0.0001) and between the increase in plasminogen activator activity and aVP levels (r = 0.56, P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Two cases of the nephrotic syndrome with a reversible coagulation defect.

Two cases of the nephrotic syndrome with an apparently identical defect of blood coagulation, discovered during preparation for renal biopsy are described. Plasma from both patients showed prolongation of thrombin and kaolin cephalin times which was probably due to abnormally slow polymerization of fibrin monomer. Corticosteroid therapy reversed the abnormal times in one case. One of the patients showed seasonal relapses which occurred in relation to episodes of hay fever associated with allergy to grass pollen. The other patient showed some similar features, but on renal biopsy was found to have proliferative glomerulonephritis.